The present invention relates to welded wire reinforcing mats for use in the manufacture of concrete pipe. In manufacturing concrete pipe, a length of fabric, comprising interwelded sets of criss-crossed strands, is cut into a suitable length and formed into a circular or elliptical cage. Often, stirrup reinforcement is added to this cage before it is cast into a concrete pipe. Individual lengths of wire, called stirrups, are individually welded or attached to the wires of the cage, generally at the crown and invert thereof. Also available are sinusoidal strands of wire which define a plurality of stirrup projections in a row. By welding several of these sinusoidal strands to the cage, one minimizes the amount of welding and stirrup members required.
In one aspect of my earlier invention disclosed in U.S. Pat. No. 3,844,511, I conceived of the concept of providing mats of ordinary fabric having a plurality of stirrups arranged in parallel rows so that an entire section of a cage could be readily reinforced with stirrups by simply forming a mat to an arcuate shape and placing it in or on the cage and welding it. One problem with that concept is that the mat must somehow be formed into the required curvilinear or arcuate configuration to conform to the curvature of the cage. This requires the use of some type of mechanical former. Mechanical forming would be particularly difficult if not impossible if hinged stirrups are not used.